Process for the preparation of a composition comprising heterophasic propylene co-polymer and talc

ABSTRACT

The invention relates to a process for the preparation of a composition comprising a heterophasic propylene copolymer, a propylene copolymer and talc, wherein the heterophasic propylene copolymer consists of (a) a propylene-based matrix, wherein the propylene-based matrix consists of a propylene homopolymer and/or a propylene-α-olefin copolymer consisting of at least 70% by mass of propylene and up to 30% by mass of α-olefin based on the total mass of the propylene-based matrix, wherein the propylene-based matrix is present in an amount of 60 to 95 wt % based on the total heterophasic propylene copolymer and (b) a dispersed ethylene-α-olefin copolymer, wherein the dispersed ethylene-α-olefin copolymer is present in an amount of 40 to 5 wt % based on the total heterophasic propylene copolymer and wherein the sum of the total amount of propylene-based matrix and total amount of the dispersed ethylene-α-olefin copolymer in the heterophasic propylene copolymer is 00 wt %, wherein the composition has a desired melt flow index in the range of 1 to 200 dg/min as measured according to ISO1133 (2.16 kg/230° C.) comprising the steps of (a) melt-mixing a propylene copolymer with a talc to obtain a masterbatch (b) melt-mixing the masterbatch with 1 the heterophasic propylene copolymer and a peroxide to obtain the composition comprising a heterophasic propylene copolymer, a propylene copolymer and talc, wherein the amount of peroxide is chosen such that a composition comprising a heterophasic propylene copolymer, a propylene copolymer and talc having the desired melt flow index is obtained.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a 371 of International Application No.PCT/EP2013/069295, filed Sep. 17, 2013 which claims priority to EuropeanApplication Nos. 12006582.6, filed Sep. 19, 2012 and 12006583.4, filedSep. 19, 2012 which are hereby incorporated by reference in theirentirety.

The invention relates to a process for the preparation of a compositioncomprising a heterophasic propylene copolymer and talc, a compositionobtained or obtainable by said process and to the use of saidcomposition.

Heterophasic propylene copolymer, also known as impact propylenecopolymers or propylene block copolymers, are an important class ofpolymers due to their attractive combination of mechanical properties,such as impact strength over a wide temperature range and their lowcost. These copolymers find a wide range of applications ranging fromthe consumer industry (for example packaging and housewares), theautomotive industry to electrical applications.

In industry, there is a continuous search for methods to modify therheology of polyolefins in liquid phase, in particular to reduce theirviscosity. The viscosity reduction is often also described as“vis-breaking”, “melt-shifting”, “modifying rheology” or “controllingrheology”. It is known that (organic) peroxides may be used to reducethe viscosity. There are different ways in which the (organic) peroxidesbehave in conventional degradation processes upon heating and meltingconditions. On the one hand, under certain process conditions, theperoxides initially decompose to produce free radicals, which thenabstract hydrogen from a tertiary carbon of the polypropylene backboneto form free radicals on the polymer, and which further recombine. Onthe other hand, peroxides initiate a breakage of the longest chains ofthe polymer molecules and, subsequently, this results in a decrease inviscosity of the polymer, an increase in melt flow rate, and a narrowermolecular weight distribution, characteristics which are directlyresponsible for improved flow properties of polypropylene in order tomake the product more suitable for certain applications.

It is known to add peroxides to the heterophasic propylene copolymer toobtain impact propylene copolymers having a higher melt flow rate. Thismakes it for example possible to obtain several impact propylenecopolymers with different melt flow rates from one and the same basegrade.

An example of such a “melt-shifting” process is described inUS2005/0277742A2. US2005/0277742A1 discloses a process for preparing acontrolled rheology propylene heterophasic copolymer by degrading apolypropylene with a linear dialkyl peroxide having a backbonecontaining at least 6 carbon atoms and a double or triple bondcomprising the steps of: either

(a) reactor polymerizing a propylene heterophasic copolymer;

(b) extruding the propylene heterophasic copolymer of step (a), withsaid linear dialkyl peroxide having a backbone containing at least 6carbon atoms and a double or triple bond, and optionally with one ormore filler(s), in an extruder, at a temperature sufficient to maintainthe copolymer in the molten state; or

(c) extruding a propylene (co)polymer with said linear dialkyl peroxidehaving a backbone containing at least 6 carbon atoms and a double ortriple bond, optionally with one or more elastomeric modifier(s) and/orone or more filler(s), in an extruder, at a temperature sufficient tomaintain the copolymer in the molten state.

To increase the stiffness of the heterophasic propylene copolymer, talcmay be added as a filler. However, when the stiffness of theheterophasic propylene copolymer is increased by talc, more peroxide isneeded in order to obtain the same increase in melt flow rate of aheterophasic propylene copolymer as compared to when talc is not presentin the heterophasic propylene copolymer. It is undesired to use highamounts of peroxides, since high amounts of typical peroxide degradationproducts, for example methane and acetone may lead to safety issuesduring the manufacturing process. Also, the use of high amounts ofperoxides adds to the cost of the heterophasic polypropylene, which isundesired from an economical point of view. Last but not least, the useof high amounts of peroxides leads to high amounts of peroxidedegradation products and impurities in the final polymer. These peroxidedegradation products may be released during the life-time of theheterophasic propylene copolymer composition, which is undesired, asthey may cause unpleasant odours and may affect organoleptic properties.Also, high amounts of peroxide degradation products make theheterophasic propylene copolymer unsuitable for food contactapplications.

Therefore, it is an object of the invention to provide a heterophasicpolypropylene composition that combines a high stiffness with a goodimpact strength and a high flow, but which does not contain a highamount of peroxide degradation products.

This object is achieved by a process for the preparation of acomposition comprising a heterophasic propylene copolymer, a propylenecopolymer and talc, wherein the heterophasic propylene copolymerconsists of

(a) a propylene-based matrix,

wherein the propylene-based matrix consists of a propylene homopolymerand/or a propylene-α-olefin copolymer consisting of at least 70% by massof propylene and up to 30% by mass of α-olefin, for example ethylene,based on the total mass of the propylene-based matrix, and wherein thepropylene-based matrix is present in an amount of 60 to 95 wt % based onthe total heterophasic propylene copolymer, and

(b) a dispersed ethylene-α-olefin copolymer, wherein the dispersedethylene-α-olefin copolymer is present in an amount of 40 to 5 wt %based on the total heterophasic propylene copolymer and wherein the sumof the total amount of propylene-based matrix and total amount of thedispersed ethylene-α-olefin copolymer in the heterophasic propylenecopolymer is 100 wt %,

wherein the composition has a desired melt flow index in the range of 1to 200 dg/min as measured according to ISO1133 (2.16 kg/230° C.),

comprising the steps of

-   -   (a) melt-mixing a propylene copolymer with a talc to obtain a        masterbatch,    -   (b) melt-mixing the masterbatch with the heterophasic propylene        copolymer and a peroxide to obtain the composition comprising a        heterophasic propylene copolymer, a propylene copolymer and        talc, wherein the amount of peroxide is chosen such that a        composition comprising a heterophasic propylene copolymer, a        propylene copolymer and talc having the desired melt flow index        is obtained.

It has been found that with the process of the present invention, aheterophasic polypropylene composition can be prepared that combines thefavourable properties of a high stiffness, a good impact strength and ahigh flow with a decreased amount of peroxide degradation products.

Furthermore, the process of the invention is an easy and cost-effectiveprocess. Also, the heterophasic polypropylene composition thus preparedmay maintain its (mechanical) properties.

For purpose of the present invention, stiffness is determined bymeasuring the flexural modulus according to ASTM D790-10. For purpose ofthe present invention, impact strength is determined by measuring theIzod impact strength at 23° C. according to ISO 180 4A. For purpose ofthe present invention, flow is determined by measuring the melt flowrate, also called melt flow index or melt index according to ISO1133(2.16 kg/230° C.).

Heterophasic propylene copolymers are generally prepared in one or morereactors, by polymerization of propylene in the presence of a catalystand subsequent polymerization of a propylene-α-olefin mixture. Theresulting polymeric materials are heterophasic, but the specificmorphology usually depends on the preparation method and monomer ratio.

The heterophasic propylene copolymers employed in the process accordingto present invention can be produced using any conventional techniqueknown to the skilled person, for example multistage processpolymerization, such as bulk polymerization, gas phase polymerization,slurry polymerization, solution polymerization or any combinationsthereof. Any conventional catalyst systems, for example, Ziegler-Nattaor metallocene may be used. Such techniques and catalysts are described,for example, in WO06/010414; Polypropylene and other Polyolefins, by Servan der Ven, Studies in Polymer Science 7, Elsevier 1990; WO06/010414,U.S. Pat. No. 4,399,054 and U.S. Pat. No. 4,472,524.

The heterophasic propylene copolymer of the composition of the inventionconsists of a propylene-based matrix and a dispersed ethylene-α-olefincopolymer. The propylene-based matrix forms the continuous phase in theheterophasic propylene copolymer.

The propylene-based matrix consists of a propylene homopolymer and/or apropylene-α-olefin copolymer consisting of at least 70% by mass ofpropylene and up to 30% by mass of α-olefin, for example ethylene, forexample consisting of at least 80% by mass of propylene and up to 20% bymass of α-olefin, for example ethylene, for example consisting of atleast 90% by mass of propylene and up to 10% by mass of α-olefin, forexample ethylene, based on the total mass of the propylene-based matrix.

Preferably, the propylene-based matrix consists of a propylenehomopolymer.

Preferably, the α-olefin in the propylene-α-olefin copolymer is selectedfrom the group of α-olefins having 2 or 4-10 carbon atoms and morepreferably the α-olefin is ethylene.

The melt flow index (MFI) of the propylene-based matrix (before it ismixed into the composition of the invention) may be in the range of forexample 0.3 to 200 dg/min, for example from 0.3 to 80 dg/min measuredaccording to ISO1133 (2.16 kg/230° C.), for example in the range from 3to 70, for example in the range from 10 to 60 dg/min, for example in therange from 15 to 40 dg/min.

The propylene-based matrix is present in an amount of 60 to 95 wt %, forexample 65 to 85 wt %, for example 70 to 85 wt %, for example 70 to 80wt %, for example 65 to 75 wt % or 75 to 85 wt % based on the totalheterophasic propylene copolymer.

The propylene-based matrix is preferably semi-crystalline, that is it isnot 100% amorphous, nor is it 100% crystalline. For example, thepropylene-based matrix is at least 40% crystalline, for example at least50%, for example at least 60% crystalline and/or for example at most 80%crystalline, for example at most 70% crystalline. For example, thepropylene-based matrix has a crystallinity of 60 to 70%. For purpose ofthe invention, the degree of crystallinity of the propylene-based matrixis measured using differential scanning calorimetry according toISO11357-1 and ISO11357-3 of 1997, using a scan rate of 10° C./min, asample of 5 mg and the second heating curve using as a theoreticalstandard for a 100% crystalline material 207.1 J/g.

Besides the propylene-based matrix, the heterophasic propylene copolymeralso consists of a dispersed ethylene-α-olefin copolymer. The dispersedethylene-α-olefin copolymer is also referred to herein as the ‘dispersedphase’. The dispersed phase is embedded in the heterophasic propylenecopolymer in a discontinuous form. The particle size of the dispersedphase is typically in the range of 0.5 to 10 microns, as may bedetermined by transmission electron microscopy (TEM).

The MFI of the dispersed ethylene-α-olefin copolymer (before it is mixedinto the composition of the invention) may for example be in the rangefrom 0.001 to 10 dg/min (measured according to ISO1133 (2.16 kg/230°C.)), preferably in the range from 0.006 to 5 dg/min.

The dispersed ethylene-α-olefin copolymer is present in an amount of 40to 5 wt %, for example in an amount of 35 to 15 wt % based on the totalheterophasic propylene copolymer, for example in an amount of at least20 wt % and/or for example in an amount of at most 30 wt % based on thetotal heterophasic propylene copolymer.

Preferably, the amount of ethylene in the ethylene-α-olefin copolymer isin the range of 20-65 wt %, for example in the range of 40 to 60 wt %based on the ethylene-α-olefin copolymer, for example the amount ofethylene in the ethylene-α-olefin copolymer is at least 30 wt % and/orfor example at most 55 wt % based on the ethylene-α-olefin copolymer.

In the heterophasic polypropylene in the composition of the invention,the sum of the total weight of the propylene-based matrix and the totalweight of the dispersed ethylene-α-olefin copolymer is 100 wt %

The α-olefin in the ethylene-α-olefin copolymer is preferably chosenfrom the group of α-olefins having 3 to 8 carbon atoms and any mixturesthereof, preferably the α-olefin in the ethylene-α-olefin copolymer ischosen from the group of α-olefins having 3 to 4 carbon atoms and anymixture thereof, more preferably the α-olefin is propylene, in whichcase the ethylene-α-olefin copolymer is ethylene-propylene copolymer.Examples of suitable α-olefins having 3 to 8 carbon atoms, which may beemployed as ethylene comonomers to form the ethylene α-olefins copolymerinclude but are not limited to propylene, 1-butene, 1-pentene,4-methyl-1-pentene, 1-hexen, 1-heptene and 1-octene.

The process of the invention comprises the steps of

(a) melt-mixing a propylene copolymer with a talc to obtain amasterbatch,

(b) melt-mixing the masterbatch with the heterophasic propylenecopolymer and a peroxide to obtain the composition comprising aheterophasic propylene copolymer, a propylene copolymer and talc.

In the process of the invention, a propylene copolymer is melt-mixedwith a talc to obtain a masterbatch. Melt-mixing may be performed bymethods known to the skilled person, for example using an extruder andthe conditions as described herein for step b).

The propylene copolymer may be any propylene copolymer, for example apropylene-α-olefin copolymer, wherein the α-olefin is selected from thegroup of α-olefins having 2 or 4-10 C-atoms and wherein the α-olefincontent is up to 10 wt % based on the propylene copolymer; or thepropylene copolymer may be a random propylene-ethylene copolymer, forexample wherein the ethylene content is up to 10 wt % based on thepropylene copolymer; or the propylene copolymer may be a propylenehomopolymer; or the propylene copolymer may be a heterophasic propylenecopolymer.

Preferably, the propylene copolymer is a heterophasic propylenecopolymer, more preferably the propylene copolymer is the sameheterophasic propylene copolymer as used in step b) of the process ofthe invention.

In a special embodiment therefore, the invention relates to a processaccording to the invention comprising the steps of

(a) melt-mixing a heterophasic propylene copolymer with a talc to obtaina masterbatch,

(b) melt-mixing the masterbatch with the same heterophasic propylenecopolymer (as used in step a)) and a peroxide to obtain the compositioncomprising the heterophasic propylene copolymer and talc.

The weight ratio of the talc to the propylene copolymer in themasterbatch is in principle not critical and may be varied between wideranges. In principle, the weight ratio of talc to the propylenecopolymer is not critical. Preferably, the weight ratio of talc topropylene copolymer in the masterbatch is from 1:9 to 9:1, morepreferably from 1:3 to 9:1, for example from 1:1 to 9:1. High weightratios of talc to propylene copolymer in the masterbatch are preferredas this decreases the volume of the masterbatch needed. A high volume ofmasterbatch is undesired as this makes it impractical for dosing to theheterophasic propylene copolymer.

Preferably, the weight ratio of the propylene copolymer used in step a),preferably a heterophasic propylene copolymer, to the heterophasicpropylene copolymer used in step b), preferably the same heterophasicpropylene copolymer (as used in step a) is 1:1 to 1:20, for example from1:5 to 1:20 or 1:5 to 1:15 or 1:5 to 1:10.

The masterbatch may contain the propylene copolymer and the talc only,but may also comprise additives and/or polar substances suitable forsurface-modification of the talc, for example as described herein, forexample ethylene-bis-stearamide.

With melt-mixing is meant that the masterbatch, the heterophasicpropylene copolymer and the peroxide are mixed at a temperature thatexceeds the melting point of the heterophasic propylene copolymer andthe propylene copolymer in the masterbatch. Melt-mixing may be doneusing techniques known to the skilled person, for example in anextruder. Generally, in the process of the invention, melt-mixing isperformed at a temperature in the range from 20-300° C.

For example, the melt-mixing of step a) of the process of the inventionmay be performed at a temperature in the range from 20-300° C.

For example, the melt-mixing of step b) of the process of the inventionmay be performed at a temperature in the range from 20-330° C.

Suitable conditions for melt-mixing, such as temperature, pressure,amount of shear, screw speed and screw design when an extruder is usedare known to the skilled person.

When using an extruder, a conventional extruder such as a twin-screwextruder may be used. The temperature can vary through the differentzones of the extruder as required. For example, the temperature may varyfrom 180° C. in the feed zone to 300° C. at the die. Preferably, thetemperature in the extruder varies from 200 to 265° C.; lowertemperatures may impede reactions between the peroxide and an optionalco-agent, for example polyfunctional monomers, such as BDDMA and, as aconsequence, compositions with the desired melt flow index may not beobtained; too high temperatures may induce undesired degradationprocesses, which may for example result in compositions having poormechanical properties. Likewise, the screw speed of the extruder may bevaried as needed. Typical screw speed are in the range from about 100rpm to about 400 rpm.

The residence time in the extruder for the heterophasic propylenecopolymer may be lower than 1 minute, for example between 10 and 40seconds.

Talc is a relatively abundant, inexpensive, highly hydrophobic andgenerally unreactive mineral. It can be categorized as a hydratedmagnesium silicate and its main components can be represented by, interalia, one or more of the formulas (Si₂O₅)₂Mg₃(OH)₂, Si₈Mg₆O₂₀(OH)₄ orMg₁₂Si₁₆O₄₀(OH)₈. Talcs suitable for use as additives to a heterophasicpropylene copolymer are commercially available from for example ImerysLuzenac. ‘Talc’ and ‘talcum’ are used interchangeably herein.

Talc is available in several particle sizes, for example the particlesizes of talc are classified as ‘ultrafine’ (average particle size oflower than 1 μm, for example an average particle size in the range of0.5 to 0.91 μm) and ‘fine’ (average particle size of at least 1 μm, forexample an average particle size of 1 μm to 5 μm). Preferably, fine orultrafine powder particles are used in the process of the presentinvention.

Depending on the desired stiffness, the amount of talc used may bevaried. For practical reasons, the amount of surface-modified talc inthe composition of the invention is preferably from 0.5 to 5 wt % basedon the total amount of propylene copolymer of step a) and theheterophasic propylene copolymer of step b). For example, the amount ofsurface-modified talc in the composition is at least 1 wt %, for exampleat least 1.5 wt % and/or for example at most 4 wt %, for example at most3.5 wt %, for example at most 3 wt % based on the propylene copolymer ofstep a) and the heterophasic propylene copolymer of step b).

Preferably, the composition that is prepared by the process of theinvention has a melt flow index in the range of 1 to 200 dg/min asmeasured according to ISO1133 (2.16 kg/230° C.). For example, the meltflow index is at least 1, for example at least 5 or for example at least14 dg/min and/or for example at most 200 dg/min, for example at most 80dg/min or for example at least 20 dg/min as measured according toISO1133 (2.16 kg/230° C.). Preferably, the melt flow index of thecomposition that is prepared by the process of the invention is in therange from 5 to 80 dg/min, for example in the range from 14 to 20 dg/minas measured according to ISO1133 (2.16 kg/230° C.).

Examples of suitable peroxides include organic peroxides having adecomposition half-life of less than 1 minute at the average processtemperature during the melt-mixing of the heterophasic propylenecopolymer with the talc and the peroxide. Suitable organic peroxidesinclude but are not limited to dialkyl peroxides, e.g. dicumylperoxides, peroxyketals, peroxycarbonates, diacyl peroxides,peroxyesters and peroxydicarbonates. Specific examples of these includebenzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide,di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(peroxybenzoato)-3-hexene,1,4-bis(tert-butylperoxyisopropyl)benzene, lauroyl peroxide, tert-butylperacetate, α,α′-bis(tert-butylperoxy)diisopropylbenzene (Luperco® 802),2,5-dimethyl-2,5-di(tert-butylperoxy)-3-hexene,2,5-dimethyl-2,5-di(tert-butylperoxy)-hexane, tert-butyl perbenzoate,tert-butyl perphenylacetate, tert-butyl per-sec-octoate, tert-butylperpivalate, cumyl perpivalate, cumene hydroperoxide, diisopropylbenzene hydroperoxide, 1,3-bis(t-butylperoxy-isopropyl)benzene, dicumylperoxide, tert-butylperoxy isopropyl carbonate and any combinationthereof. Preferably, a dialkyl peroxides is employed in the processaccording to the present invention. More preferably, the peroxide isα,α′-bis-(tert-butylperoxy)diisopropylbenzene,2,5-dimethyl-2,5-di(tert-butylperoxy)-hexane or3,6,9-Triethyl-3,6,9-trimethyl-1,4,7-triperoxonane. Preferably, theperoxide is selected from the group of non-aromatic peroxides.

It can easily be determined by the person skilled in the art throughroutine experimentation how much peroxide should be used to obtain acomposition having the desired melt flow index. This also depends on thehalf-life of the peroxide and on the conditions used for themelt-mixing, which in turn depend on the exact composition. Typically,the amount of peroxide used will lie in the range of 0.02 to 0.5 wt %based on the heterophasic propylene copolymer.

In the process of the invention or in the composition of the inventionat least part of the talc may be surface-modified, that means thatmixtures of surface-modified talc with non-surface modified talc mayalso be used. Preferably, at least 80 wt % of the talc used in theprocess of the invention or present in the composition of the inventionis surface-modified, more preferably at least 90 wt %, even morepreferably at least 95 wt %, in particular at least 98 wt %, more inparticular at least 99 wt %, most in particular all talc used in theprocess of the invention or present in the composition of the inventionis surface-modified.

Other words that are commonly used for surface-modified talc aresurface-treated talc, coated talc. Surface-modified talcs are known tothe person skilled in the art and are commercially available from forexample Imerys Luzenac. Surface-modified talcs may be prepared by addinga surface modifier to the talc. The nature and concentration of themodifier depends on the desired benefit in the final talc composite,like improvement of the bond between the talcum and polymer or toimprove the dispersion of the talc in the polymer. Examples of surfacemodifiers are silanes, amines, glycols, stearates, sorbates andtitanates.

Preferably, the surface-modified talc is a talc that is surface-modifiedwith a polar substance selected from the group of glycols, silanes andamines

In a special embodiment, the invention relates to a process of theinvention, wherein the surface-modified talc is prepared by mixing of atalc with a polar substance, preferably ethylene-bis-stearamide. Thismay be done off-line (i.e. prior to melt-mixing the talc and thepropylene copolymer) or the surface-modified talc may be prepared insitu (i.e. by adding the polar substance together with the talc in themelt-mixing step).

Without wishing to be bound be theory, it is believed that by mixing thetalc with a polar substance, the talc can be ‘coated’ in situ.

Examples of the polar substances are as described herein. Preferably,the mixing of talc is done with ethylene-bis-stearamide (also referredto as EBS or EBA).

In another aspect, the invention relates to a composition obtained orobtainable by the process of the invention.

Specifically, the invention relates to a composition comprising aheterophasic propylene copolymer, a propylene copolymer and talc,wherein the heterophasic propylene copolymer consists of

(a) a propylene-based matrix, wherein the propylene-based matrixconsists of a propylene homopolymer and/or a propylene-α-olefincopolymer consisting of at least 70% by mass of propylene and up to 30%by mass of α-olefin, for example ethylene, based on the total mass ofthe propylene-based matrix, wherein the propylene-based matrix ispresent in an amount of 60 to 95 wt % based on the total heterophasicpropylene copolymer, and

(b) a dispersed ethylene-α-olefin copolymer, wherein the dispersedethylene-α-olefin copolymer is present in an amount of 40 to 5 wt %based on the total heterophasic propylene copolymer and wherein the sumof the total amount of propylene-based matrix and total amount of thedispersed ethylene-α-olefin copolymer in the heterophasic propylenecopolymer is 100 wt %,

wherein the composition has a desired melt flow index in the range of 1to 200 dg/min as measured according to ISO1133 (2.16 kg/230° C.), and

wherein the amount of volatile organic compounds as measured through theVOC-value according to VDA278 (30 min, 180° C.) and determined by gaschromatography is less than 1500 ppm based on the total composition.

For purpose of the invention when reference is made to standard VDA278,the version of October 2011 is referred to.

Preferably, the amount of volatile organic compounds (VOC-value) asmeasured through the VOC-value according to VDA278 (30 min, 180° C.) anddetermined by gas chromatography (version October 2011) is less than1300 ppm, more preferably less than 1000 ppm, for example less than 750ppm, for example less than 600 ppm, for example less than 500 ppm, forexample less than 400 ppm, for example less than 300 ppm based on thetotal composition

In another embodiment, the invention relates to a composition comprisinga heterophasic propylene copolymer, a propylene copolymer and talc,wherein the heterophasic propylene copolymer consists of

(a) a propylene-based matrix, wherein the propylene-based matrixconsists of a propylene homopolymer and/or a propylene-α-olefincopolymer consisting of at least 70% by mass of propylene and up to 30%by mass of α-olefin, for example ethylene, based on the total mass ofthe propylene-based matrix, and wherein the propylene-based matrix ispresent in an amount of 60 to 95 wt % based on the total heterophasicpropylene copolymer, and

(b) a dispersed ethylene-α-olefin copolymer, wherein the dispersedethylene-α-olefin copolymer is present in an amount of 40 to 5 wt %based on the total heterophasic propylene copolymer and wherein the sumof the total amount of propylene-based matrix and total amount of thedispersed ethylene-α-olefin copolymer in the heterophasic propylenecopolymer is 100 wt %, wherein the composition has a desired melt flowindex in the range of 1 to 200 dg/min as measured according to ISO1133(2.16 kg/230° C.), wherein the amount of volatile compounds (FOG-value)as measured through the FOG-value according to VDA278 on the secondheating (first heating 30 min at 90° C., second heating 1 hour at 120°C.) is less than 500 ppm, for example less than 400 ppm, for exampleless than 350 ppm, for example less than 300 ppm, for example less than250 ppm, for example less than 200 ppm, for example less than 150 ppm.

In another aspect, the invention relates to a composition comprising aheterophasic propylene copolymer, a propylene copolymer and talc,wherein the heterophasic propylene copolymer consists of

(a) a propylene-based matrix, wherein the propylene-based matrixconsists of a propylene homopolymer and/or a propylene-α-olefincopolymer consisting of at least 70% by mass of propylene and up to 30%by mass of α-olefin, for example ethylene, based on the total mass ofthe propylene-based matrix, wherein the propylene-based matrix ispresent in an amount of 60 to 95 wt % based on the total heterophasicpropylene copolymer, and

(b) a dispersed ethylene-α-olefin copolymer, wherein the dispersedethylene-α-olefin copolymer is present in an amount of 40 to 5 wt %based on the total heterophasic propylene copolymer and wherein the sumof the total amount of propylene-based matrix and total amount of thedispersed ethylene-α-olefin copolymer in the heterophasic propylenecopolymer is 100 wt %, wherein the composition has a desired melt flowindex in the range of 1 to 200 dg/min as measured according to ISO1133(2.16 kg/230° C.), wherein the amount of butanol emitted as measuredusing VDA 278 (10 min, 180° C.) as determined with gaschromatography-mass spectrometry (GC-MS) is less than 100 ppm, forexample less than 80 ppm, for example less than 70 ppm, for example lessthan 60 ppm, for example less than 50 ppm, for example less than 40 ppm,for example less than 30 ppm.

Such composition having an amount of butanol of less than 100 ppm,preferably less than 80 ppm, more preferably less than 60 ppm, mostpreferably less than 40 ppm based on the total composition is especiallysuitable for use in food contact applications.

Therefore, the invention also relates to the use of a compositioncomprising a heterophasic propylene copolymer, a propylene copolymer andtalc, wherein the heterophasic propylene copolymer consists of

(a) a propylene-based matrix, wherein the propylene-based matrixconsists of a propylene homopolymer and/or a propylene-α-olefincopolymer consisting of at least 70% by mass of propylene and up to 30%by mass of α-olefin, for example ethylene, based on the total mass ofthe propylene-based matrix, wherein the propylene-based matrix ispresent in an amount of 60 to 95 wt % based on the total heterophasicpropylene copolymer, and

(b) a dispersed ethylene-α-olefin copolymer, wherein the dispersedethylene-α-olefin copolymer is present in an amount of 40 to 5 wt %based on the total heterophasic propylene copolymer and wherein the sumof the total amount of propylene-based matrix and total amount of thedispersed ethylene-α-olefin copolymer in the heterophasic propylenecopolymer is 100 wt %, wherein the composition has a desired melt flowindex in the range of 1 to 200 dg/min as measured according to ISO1133(2.16 kg/230° C.), wherein the amount of butanol emitted as measuredusing VDA 278 (10 min, 180° C.) as determined with gaschromatography-mass spectrometry (GC-MS) is less than 100 ppm, forexample less than 80 ppm, for example less than 70 ppm, for example lessthan 60 ppm, for example less than 50 ppm, for example less than 40 ppm,for example less than 30 ppm in food contact applications.

In another aspect, the invention relates to a composition comprising aheterophasic propylene copolymer, a propylene copolymer and talc,wherein the heterophasic propylene copolymer consists of

(a) a propylene-based matrix, wherein the propylene-based matrixconsists of a propylene homopolymer and/or a propylene-α-olefincopolymer consisting of at least 70% by mass of propylene and up to 30%by mass of α-olefin, for example ethylene, based on the total mass ofthe propylene-based matrix, wherein the propylene-based matrix ispresent in an amount of 60 to 95 wt % based on the total heterophasicpropylene copolymer, and

(b) a dispersed ethylene-α-olefin copolymer, wherein the dispersedethylene-α-olefin copolymer is present in an amount of 40 to 5 wt %based on the total heterophasic propylene copolymer and wherein the sumof the total amount of propylene-based matrix and total amount of thedispersed ethylene-α-olefin copolymer in the heterophasic propylenecopolymer is 100 wt %, wherein the composition has a desired melt flowindex in the range of 1 to 200 dg/min as measured according to ISO1133(2.16 kg/230° C.), wherein the amount of acetone emitted as measuredusing VDA 278 (10 min, 180° C.) as determined with gaschromatography-mass spectrometry (GC-MS) is less than 4 ppm, for exampleless than 3 ppm, for example less than 2 ppm, for example less than 1ppm.

In another aspect, the invention relates to a composition comprising aheterophasic propylene copolymer, a propylene copolymer and talc,wherein the heterophasic propylene copolymer consists of

(a) a propylene-based matrix, wherein the propylene-based matrixconsists of a propylene homopolymer and/or a propylene-α-olefincopolymer consisting of at least 70% by mass of propylene and up to 30%by mass of α-olefin, for example ethylene, based on the total mass ofthe propylene-based matrix, wherein the propylene-based matrix ispresent in an amount of 60 to 95 wt % based on the total heterophasicpropylene copolymer, and

(b) a dispersed ethylene-α-olefin copolymer, wherein the dispersedethylene-α-olefin copolymer is present in an amount of 40 to 5 wt %based on the total heterophasic propylene copolymer and wherein the sumof the total amount of propylene-based matrix and total amount of thedispersed ethylene-α-olefin copolymer in the heterophasic propylenecopolymer is 100 wt %, wherein the composition has a desired melt flowindex in the range of 1 to 200 dg/min as measured according to ISO1133(2.16 kg/230° C.), wherein the amount of isopropenylacetylbenzene asmeasured using VDA278 (10 min, 180° C.) as determined with gaschromatography-mass spectrometry (GC-MS) is less than 20, for exampleless than 15, for example less than 10 ppm based on the totalcomposition, and/or wherein the amount of diacetylbenzene as measuredusing VDA278 (10 min, 180° C.) as determined with gaschromatography-mass spectrometry (GC-MS) is less than 90, for exampleless than 80, for example less than 30, for example less than 25 ppm.

The invention also relates a composition comprising a heterophasicpropylene copolymer, a propylene copolymer and talc, wherein theheterophasic propylene copolymer consists of

(a) a propylene-based matrix, wherein the propylene-based matrixconsists of a propylene homopolymer and/or a propylene-α-olefincopolymer consisting of at least 70% by mass of propylene and up to 30%by mass of α-olefin, for example ethylene, based on the total mass ofthe propylene-based matrix, wherein the propylene-based matrix ispresent in an amount of 60 to 95 wt % based on the total heterophasicpropylene copolymer, and

(b) a dispersed ethylene-α-olefin copolymer, wherein the dispersedethylene-α-olefin copolymer is present in an amount of 40 to 5 wt %based on the total heterophasic propylene copolymer and wherein the sumof the total amount of propylene-based matrix and total amount of thedispersed ethylene-α-olefin copolymer in the heterophasic propylenecopolymer is 100 wt %, wherein the composition has a desired melt flowindex in the range of 1 to 200 dg/min as measured according to ISO1133(2.16 kg/230° C.), and

wherein the amount of volatile organic compounds as measured through theVOC-value according to VDA278 (30 min, 180° C.) and determined by gaschromatography is less than 1500 ppm, preferably less than 1300 ppm,more preferably less than 1000 ppm, for example less than 750 ppm, forexample less than 600 ppm, for example less than 500 ppm, for exampleless than 400 ppm, for example less than 300 ppm based on the totalcomposition, and/or wherein the amount of volatile compounds (FOG-value)as measured through the FOG-value according to VDA278 on the secondheating (first heating 30 min at 90° C., second heating 1 hour at 120°C.) is less than 500 ppm, for example less than 400 ppm, for exampleless than 350 ppm, for example less than 300 ppm, for example less than250 ppm, for example less than 200 ppm, for example less than 150 ppm,and/or wherein the amount of butanol emitted as measured using VDA 278(10 min, 180° C.) as determined with gas chromatography-massspectrometry (GC-MS) is less than 100 ppm, for example less than 80 ppm,for example less than 70 ppm, for example less than 60 ppm, for exampleless than 50 ppm, for example less than 40 ppm, for example less than 30ppm. and/or wherein the amount of acetone emitted as measured using VDA278 (10 min, 180° C.) as determined with gas chromatography-massspectrometry (GC-MS) is less than 4 ppm, for example less than 3 ppm,for example less than 2 ppm, for example less than 1 ppm, and/or whereinthe amount of isopropenylacetylbenzene as measured using VDA278 (10 min,180° C.) as determined with gas chromatography-mass spectrometry (GC-MS)is less than 20, for example less than 15, for example less than 10 ppmbased on the total composition, and/or wherein the amount of diacetylbenzene as measured using VDA278 (10 min, 180° C.) as determined withgas chromatography-mass spectrometry (GC-MS) is less than 90, forexample less than 80, for example less than 30, for example less than 25ppm, preferably wherein the amount of isopropenylacetylbenzene asmeasured using VDA278 (10 min, 180° C.) as determined with gaschromatography-mass spectrometry (GC-MS) is less than 20, for exampleless than 15, for example less than 10 ppm based on the totalcomposition and/or wherein the amount of diacetyl benzene as measuredusing VDA278 (10 min, 180° C.) as determined with gaschromatography-mass spectrometry (GC-MS) is less than 90, for exampleless than 80, for example less than 30, for example less than 25 ppm.

More in particular, the invention relates to a composition obtained orobtainable by the process of the invention

wherein the amount of volatile organic compounds as measured through theVOC-value according to VDA278 (30 min, 180° C.) and determined by gaschromatography is less than 1500 ppm, preferably less than 1300 ppm,more preferably less than 1000 ppm, for example less than 750 ppm, forexample less than 600 ppm, for example less than 500 ppm, for exampleless than 400 ppm, for example less than 300 ppm based on the totalcomposition, and/or

wherein the amount of volatile compounds (FOG-value) as measured throughthe FOG-value according to VDA278 on the second heating (first heating30 min at 90° C., second heating 1 hour at 120° C.) is less than 500ppm, for example less than 400 ppm, for example less than 350 ppm, forexample less than 300 ppm, for example less than 250 ppm, for exampleless than 200 ppm, for example less than 150 ppm, and/or

wherein the amount of butanol emitted as measured using VDA 278 (10 min,180° C.) as determined with gas chromatography-mass spectrometry (GC-MS)is less than 100 ppm, for example less than 80 ppm, for example lessthan 70 ppm, for example less than 60 ppm, for example less than 50 ppm,for example less than 40 ppm, for example less than 30 ppm, and/or

wherein the amount of acetone emitted as measured using VDA 278 (10 min,180° C.) as determined with gas chromatography-mass spectrometry (GC-MS)is less than 4 ppm, for example less than 3 ppm, for example less than 2ppm, for example less than 1 ppm and/or wherein the amount ofisopropenylacetylbenzene as measured using VDA278 (10 min, 180° C.) asdetermined with gas chromatography-mass spectrometry (GC-MS) is lessthan 20, for example less than 15, for example less than 10 ppm based onthe total composition, and/or

wherein the amount of diacetyl benzene as measured using VDA278 (10 min,180° C.) as determined with gas chromatography-mass spectrometry (GC-MS)is less than 30, for example less than 25 ppm, preferably

wherein the amount of isopropenylacetylbenzene as measured using VDA278(10 min, 180° C.) as determined with gas chromatography-massspectrometry (GC-MS) is less than 20, for example less than 15, forexample less than 10 ppm based on the total composition and/or whereinthe amount of diacetyl benzene as measured using VDA278 (10 min, 180°C.) as determined with gas chromatography-mass spectrometry (GC-MS) isless than 90, for example less than 80, for example less than 30, forexample less than 25 ppm.

For purpose of the invention, the VOC-value, the FOG-value, the amountof butanol emitted, the amount of acetone emitted and the amount ofisopropenylacetylbenzene and the amount of diacetyl benzene are measuredon a sample taken within 1 hour after it was prepared by melt-mixing andstored in airtight bags for no longer than 24 hours at a maximum of 23°C.

The compositions of the invention may further comprise additives Forexample, the compositions may further contain nucleating agents,clarifiers, stabilizers, release agents, pigments, dyes, plasticizers,anti-oxidants, antistatics, scratch resistance agents, high performancefillers, impact modifiers, flame retardants, blowing agents, recyclingadditives, coupling agents, anti microbials, anti-fogging additives,slip additives, anti-blocking additives, polymer processing aids such aslubricants and the like, etc., surface tension modifiers, co-agents, forexample 1,4-butanediol dimethacrylate (BDDMA), acrylate or methacrylate;components that enhance interfacial bonding between the polymer and thetalc, for example maleated polypropylene etc. Such additives are wellknown in the art. The skilled person can readily select any suitablecombination of additives and additive amounts without undueexperimentation. The amount of additives depends on their type andfunction. Typically, their amounts will be from 0 to 30 wt %, forexample from 0 to 20 wt %, for example from 0 to 10 wt % or from 0 to 5wt % based on the total composition.

The sum of all components added in the process of the invention to formthe composition comprising a heterophasic propylene copolymer and talcshould add up to 100% by weight.

Some or all of the components may be pre-mixed with the polypropylenecopolymer, prior to melt-mixing the heterophasic polypropylene with thetalc or they may be added to the melt-mixing step a). In casemelt-mixing occurs in the extruder, the components may be added in anyorder and by any conventional means, for example at the same ordifferent sites of the extruder.

In another aspect, the invention relates to the use of the compositionsof the invention in injection moulding, blow moulding, extrusionmoulding, compression moulding, thin-walled injection moulding, etc, forexample in food contact applications.

In yet another aspect, the invention relates to a shaped articlecomprising the composition of the invention.

The composition of the invention may be transformed into shaped(semi)-finished articles using a variety of processing techniques.Examples of suitable processing techniques include injection moulding,injection compression moulding, thin wall injection moulding, extrusion,and extrusion compression moulding. Injection moulding is widely used toproduce articles such as for example caps and closures, batteries,pails, containers, automotive exterior parts like bumpers, automotiveinterior parts like instrument panels, or automotive parts under thebonnet. Extrusion is for example widely used to produce articles, suchas rods, sheets, films and pipes. Thin wall injection moulding may forexample be used to make thin wall packaging.

The shaped article of the invention also has the advantage of lowVOC-value and/or a low FOG-value and/or a low amount of acetone and/or alow amount of butanol and/or a low amount of isopropenylacetylbenzeneand/or a low amount of diacetylbenzene.

Although the invention has been described in detail for purposes ofillustration, it is understood that such detail is solely for thatpurpose and variations can be made therein by those skilled in the artwithout departing from the spirit and scope of the invention as definedin the claims.

It is further noted that the invention relates to all possiblecombinations of features described herein, preferred in particular arethose combinations of features that are present in the claims.

It is further noted that the term ‘comprising’ does not exclude thepresence of other elements. However, it is also to be understood that adescription on a product comprising certain components also discloses aproduct consisting of these components. Similarly, it is also to beunderstood that a description on a process comprising certain steps alsodiscloses a process consisting of these steps.

The invention is now elucidated by way of the following examples,without however being limited thereto.

EXAMPLES Measurement Methods

The VOC emission was measured according to VDA278 (version October 2011;180° C., 30 min) on the granulated compounds.

The FOG emission was measured according to VDA278 (version October 2011;first heating 90° C., 30 min, second heating 1 hour at 120° C.).

The amount of isopropenylacetylbenzene was measured using VDA278 (10 minat 180° C.) and determined with GC-MS.

The amount of diacetylbenzene was measured using VDA278 (10 min at 180°C.) and determined with GC-MS.

For purpose of the present invention, stiffness is determined bymeasuring the flexural modulus according to ASTM D790-10. Flexuralmodulus was determined on 3.2 mm thick specimens according to ISO37/2,parallel orientation.

For purpose of the present invention, impact strength is determined bymeasuring the Izod impact strength at 23° C. according to ISO 180 4A,Test geometry: 65*12.7*3.2 mm, notch 45° according to ISO 37/2perpendicular orientation.

For purpose of the present invention, flow is determined by measuringthe melt flow rate, also called melt flow index or melt index accordingto ISO1133 (2.16 kg/230° C.).

Method

Several samples were prepared using a starting material having a meltflow index (MFI) of 1.5. This material is a propylene heterophasiccopolymer having a propylene polymer matrix wherein the propylene-basedmatrix (in this case a propylene homopolymer) is present in an amount of75 wt % based on the total heterophasic propylene copolymer and 25 wt %of an ethylene-propylene copolymer consisting of 55 wt % of ethylene.

Talcum masterbatch was prepared by dosing Steamic T1CF talc (uncoatedtalc) or Steamic T1DF talc (coated talc) (3.4 kg) via a separate feederin a 1:1 weight ratio with part of the heterophasic propylene copolymer(3.7 kg) and the stabilizer Irganox B225 (0.5 wt %). Steamic T1CF andSteamic T1DF were provided by Imerys Luzenac. Two talcum masterbatcheswere prepared: one with 0.3 wt % ethylene-bis-stearamide (EBA) and onewithout ethylene-bis-stearamide.

A mixture of the processing aid calcium stearate (0.05 wt %), thestabilizer Irganox B225 (0.5 wt %), the peroxide (Luperco 802PP40, whichis di(tert-butylperoxyisopropylbenzene) and heterophasic propylenecopolymer was mixed prior to dosing it to the hopper of the extruder.

The talcum masterbatch was dosed to the extruder via a separate feederto the mixture described above.

The remaining heterophasic propylene copolymer (3.3 kg) was extruded ina twin screw ZE21 extruder with one of the talcum masterbatches or withSteamic T1CF talc and the additive mixture containing the peroxide(Luperco 802PP40, which is di(tert-butylperoxyisopropylbenzene, obtainedfrom Imerys Luzenac). The amount and composition of the additive mixturewas chosen such that the amount of calcium stearate in the finalcomposition was 500 ppm (based on the total composition) and the amountof Irganox B225 was 5000 ppm (based on the total composition). Theperoxide concentration in the additive mixture was adjusted to controlthe melt flow index of the finished material to the desired value. Theamount of talc in the talcum masterbatch was chosen such that the amountof talc in the finished material was 0; 2.5 or 5 wt % based on the totalcomposition.

A typical temperature profile in the extruder is20-20-40-100-170-230-240-240-240° C., at a throughput of 2.5 kg/h at 300rpm.

The sample compositions differed on the way the talcum was introducedinto the composition (via masterbatch or directly in the extruder). Forsample number 1, the talcum used was Steamic T1CF (uncoated), introducedvia a masterbatch. For sample number 2, the talcum used was Steamic T1CF (uncoated, introduced via a masterbatch containing 0.3 wt % EBA. Forcomparative sample A, the talcum used was Steamic T1CF, which wasintroduced directly into the extruder.

Example 1

The talc concentration in the compositions was varied and the peroxideconcentration in the powder/additive mixture was adjusted to control themelt flow index to 18 dg/min.

Table 1 shows the amount of peroxide that is needed to obtain a meltflow index as determined as described herein of 18 dg/min.

TABLE 1 Required amount of peroxide concentration to shift the MFI ofthe heterophasic propylene copolymer from 1.5 to 18 dg/min RequiredRequired Required peroxide peroxide peroxide concentration concentrationconcentration at a talcum at a talcum at a talcum process concentrationof concentration of concentration of Ex. description 0 wt % (wt %) 2.5wt % (wt %) 5 wt % (wt %) 1 Masterbatch 0.16 0.18 0.25 T1CF 2masterbatch 0.16 0.16 0.16 T1CF + EBA A T1CF directly 0.16 0.20 0.45 toextruder

Conclusion 1

As can be seen from the results in table 1, the amount of peroxide thatis needed to shift the MFI of Sabic® PP PHC27 to 18 dg/min isconsiderably higher for comparative sample A, than for the compositionsof the invention (which add talc in the form of a masterbatch to theheterophasic propylene copolymer in the extruder instead of directly tothe heterophasic propylene copolymer in the extruder). It can also beseen that preferably, the talc is coated in situ, that is preferably EBAis mixed with the talc in the masterbatch, prior to extrusion of themasterbatch with the heterophasic propylene copolymer.

Example 2 Determination of the Amount of Peroxide Decomposition Products

The amount of peroxide decomposition products (diacetylbenzene andisopropenylacetylbenzene) of the compositions of examples 1, 2comparative example A and comparative example B (without talc) weredetermined in the final composition using the method described above.The tert-butanol, acetone and methane concentrations were calculated.The results are presented in Table 2 below.

TABLE 2 Amount of peroxide degradation products Isopropenyl tBuOHAcetone Methane diacetylbenzene Acetylbenzene Ex. talc (ppm) (ppm) (ppm)(ppm) (ppm) 1 Masterbatch 40 2 5 30 14 T1CF 2 Masterbatch 26 1 3 22 9T1CF + EBA A T1CF 72 4 9 37 21 directly to extruder B Without talc 26 13 27 10

Conclusion 2

As can be seen from Table 2, the amount of peroxide degradation productsin the compositions of the invention (prepared using a masterbatch) isconsiderably lower than in the composition of comparative sample A.Furthermore, in situ coating of the talc in the masterbatch by mixing inEBA further reduces the amount of peroxide degradation products in thecompositions of the invention. This has the advantage for organolepticperformance, lower emission levels and less safety issues.

Example 3 Determination of the Mechanical Properties

The Izod impact at 23° C. and the modulus II at 23° C. were alsomeasured. The results are presented in Table 3.

TABLE 3 Izod impact and flexural modulus of the heterophasic propylenecopolymer Sabic ® PP PHC27 having an MFI of 18 dg/min, using differenttalcs. 0 wt % talc 2.5 wt % talc 5 wt % talc Imp. Mod. Imp. Mod. Imp.Mod. Ex. (kJ/m2) (MPa) (kJ/m2) (MPa) (kJ/m2) (MPa) 1 M — — 65.49 115764.92 1232 2 M + E — — 62.64 1134 63.30 1228 A D — — 64.99 1134 65.201190 B No talc 60.8 993 — — — — M = masterbatch M + E = masterbatch with0.3 wt % EBA D = talc added directly to the extruder without beingpresent in the masterbatch Imp. = Izod impact at 23° C. (kJ/m²) Mod. =Flexural modulus II at 23° C. (MPa)

Conclusion 3

As can be seen from the results in Table 3, even though different talcswere used and the amount of peroxides used is less for samples 1-3 thanfor comparative sample A, the Izod impact and flexural modulus remainthe same.

This shows that the mechanical properties of the composition of theinvention even though containing a lower amount of peroxidedecomposition products remain comparable to those of compositioncontaining considerably higher amounts of peroxide decompositionproducts.

1. A process for the preparation of a composition comprising a heterophasic propylene copolymer and talc, wherein the heterophasic propylene copolymer consists of (a) a propylene-based matrix, wherein the propylene-based matrix consists of a propylene homopolymer and/or a propylene-α-olefin copolymer consisting of at least 70% by mass of propylene and up to 30% by mass of ethylene, based on the total mass of the propylene-based matrix wherein the propylene-based matrix is present in an amount of 60 to 95 wt % based on the total heterophasic propylene copolymer, and (b) a dispersed ethylene-α-olefin copolymer, wherein the dispersed ethylene-α-olefin copolymer is present in an amount of 40 to 5 wt % based on the total heterophasic propylene copolymer and wherein the sum of the total amount of propylene-based matrix and total amount of the dispersed ethylene-α-olefin copolymer in the heterophasic propylene copolymer is 100 wt %, wherein the composition has a desired melt flow index in the range of 1 to 200 dg/min as measured according to ISO1133 (2.16 kg/230° C.), wherein at least part of the talc is surface-modified and wherein the amount of talc in the composition is from about 0.5 to at most 5 wt % based on the heterophasic propylene copolymer, comprising the step of (a) melt-mixing the heterophasic propylene copolymer with the talc and a peroxide, wherein the amount of peroxide is chosen such that a composition comprising a heterophasic propylene copolymer and talc having the desired melt flow index is obtained, wherein the α-olefin in the propylene-α-olefin copolymer is selected from the group of α-olefins having 2 or 4-10 carbon atoms, wherein the amount of ethylene in the ethylene-α-olefin copolymer is in the range of 20-65 wt % based on the ethylene-α-olefin copolymer, and wherein the α-olefin in the ethylene-α-olefin copolymer is chosen from the group of α-olefins having 3 to 8 carbon atoms and any mixtures thereof.
 2. A process according to claim 1, wherein the amount of ethylene in the ethylene-α-olefin copolymer is in the range of 20-65 wt % based on the ethylene-α-olefin copolymer.
 3. A process according to claim 1, wherein the propylene-based matrix consists of a propylene homopolymer.
 4. A process according to claim 1, wherein the α-olefin in the ethylene-α-olefin copolymer is chosen from the group of α-olefins having 3 to 8 carbon atoms and any mixtures thereof.
 5. A process according to claim 1, wherein the α-olefin in the ethylene-α-olefin copolymer is propylene.
 6. A process according to claim 1, wherein the surface-modified talc is a talc that is surface-modified with a polar substance selected from the group of glycols, silanes and amines.
 7. A process according to claim 1, wherein all talc used in the process is surface-modified.
 8. A process according to claim 1, wherein the peroxide is α,α′-bis-(tert-butylperoxy)diisopropylbenzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)-hexane or 3,6,9-Triethyl-3,6,9-trimethyl-1,4,7-triperoxonane.
 9. A process according to claim 1, wherein the surface-modified talc is prepared by mixing of a talc with a polar substance.
 10. A process according to claim 9, wherein the polar substance is ethylene-bis-stearamide.
 11. A composition obtained or obtainable by the process of claim
 1. 12. A composition comprising a heterophasic propylene copolymer and talc, wherein the heterophasic propylene copolymer consists of (a) a propylene-based matrix, wherein the propylene-based matrix consists of a propylene homopolymer and/or a propylene-α-olefin copolymer consisting of at least 70% by mass of propylene and up to 30% by mass of α-olefin, based on the total mass of the propylene-based matrix, wherein the propylene-based matrix is present in an amount of 60 to 95 wt % based on the total heterophasic propylene copolymer, and (b) a dispersed ethylene-α-olefin copolymer, wherein the dispersed ethylene-α-olefin copolymer is present in an amount of 40 to 5 wt % based on the total heterophasic propylene copolymer and wherein the sum of the total amount of propylene-based matrix and total amount of the dispersed ethylene-α-olefin copolymer in the heterophasic propylene copolymer is 100 wt %, wherein the composition has a desired melt flow index in the range of 1 to 200 dg/min as measured according to ISO1133 (2.16 kg/230° C.), wherein at least part of the talc is surface-modified and wherein the amount of talc in the composition is from about 0.5 to at most 5 wt % based on the heterophasic propylene copolymer, and wherein the amount of volatile organic compounds as measured through the VOC-value according to VDA278 (30 min, 180° C.) and determined by gas chromatography is less than 1500 ppm, based on the total composition, and/or wherein the amount of volatile compounds (FOG-value) as measured through the FOG-value according to VDA278 on the second heating (first heating 30 min at 90° C., second heating 1 hour at 120° C.) is less than 500 ppm, and/or wherein the amount of butanol emitted as measured using VDA 278 (10 min, 180° C.) as determined with gas chromatography-mass spectrometry (GC-MS) is less than 100 ppm, and/or wherein the amount of acetone emitted as measured using VDA 278 (10 min, 180° C.) as determined with gas chromatography-mass spectrometry (GC-MS) is less than 4 ppm, and/or wherein the amount of isopropenylacetylbenzene as measured using VDA278 (10 min, 180° C.) as determined with gas chromatography-mass spectrometry (GC-MS) is less than 20, based on the total composition, and/or wherein the amount of diacetyl benzene as measured using VDA278 (10 min, 180° C.) as determined with gas chromatography-mass spectrometry (GC-MS) is less than 30, wherein the α-olefin in the propylene-α-olefin copolymer is selected from the group of α-olefins having 2 or 4-10 carbon atoms, wherein the amount of ethylene in the ethylene-α-olefin copolymer is in the range of 20-65 wt % based on the ethylene-α-olefin copolymer, and wherein the α-olefin in the ethylene-α-olefin copolymer is chosen from the group of α-olefins having 3 to 8 carbon atoms and any mixtures thereof.
 13. The composition according to claim 11, further comprising additives.
 14. (canceled)
 15. A shaped article comprising the composition of claim
 11. 16. A method for forming a shaped article, comprising: moulding the composition of claim 11, wherein the moulding is injection moulding, blow moulding, extrusion moulding, compression moulding or thin-walled injection moulding. 